Die-casting machine



Jan. 14 1941.

J. PULAK DIE-CASTING MACHINE Filed Nov. '7, 193B Patente Jan. 14, 1941STATES PATENT oFFlce .inplannen Navember v, 193s, serial No. cease-i InCzechoslovakia November 11, 1937 1` Claim.

For shutting off the pressure space of hydraulically operateddie-casting and like machines an ele-r ment is provided, which is movedeither trans versely or perpendicularly with respect to the direction ofmotion of the press piston. The invention relates to a mode of operationfor such die-casting machines with a hydraulically operated closingelement of the pressure space and has for its object hrmly to securethis closing element in its closed position during the casting operationand thus to prevent the press piston lifting the closing element throughthe intermediary of the metal present in the pressure space and themetal escaping not oily into the mould, but also into the atmosphere.

'The invention consists in this, that the pressure prevailing in thecylinder of the closing element, after reaching a predetermined height,initiates the motion of the press piston. This motion can thus onlyoccur, until the pressure in the cylinder of the closing elementabsolutely prevents a yielding or lifting of the latter out of itsclosed position, owing to the eiect of the pressing pressure. Withadvantage the motion of the closing piston up to the moment of closingof the pressure space is effected by the accumulator pressure used foroperating the machine, whilst the greater power required for keeping theclosing element in its closed position during the casting operation isobtained through the interposition o: a hydraulic pressure intensifierwhich also releases the motion of the press piston.

In the accompanying drawing a constructional example of an installationof a die-casting ma-.

chine according to the invention is -shown diagrammatically.

In this drawing I is the pressure space which is to be lled with thecasting material, 2 the closing element with the piston 3, 4 thehydraulic cylinder for the latter, 5 the pressure intensifier, 6 thehydraulic cylinder with the press piston 'I, 8 a normal two-valvecontrol apparatus with a non-return valve, 9 a normal two-valve controlapparatus, II) a normal two-valve control apparatus which is inuenced bythe higher pressure in the cylinder 4, II a normal two-valve control 4apparatus containing a non-return valve, I2 the l i hydraulic cylinderfor displacing the movable half of the mould and I3 a non-return valve.

The mode of operation is as follows: By actual;m ing the foot lever I4at the control apparatus B the driving medium passes with accumulatorpressure by way of the space above the piston in the pressureintensifier to the cylinder 4, the piston 3 lof which moves downwardsuntil it bears against the edge of the pressure space i. Shortly beforethis the piston collar la has actuated the adjusting lever I6 of thecontrol apparatus .5 and has thereby conveyed water under pressure tothe under side of the piston in the pressure intensiiler 5. 5 Thiscauses an increased pressure in the annular space of the pressureintensifier, which, owing to the provision of the non-return valve inthe control apparatus il, cannot be propagated to the accumulator. Thispressure, however, becomes lo operative in the cylinder 4, itspredetermined maximum value acting on the piston 3 'for securely keepingthe closing element 2 in the closed position. This increased liquidpressure however also occurs in the cylinder Il of the control ap- 15paratus Ill and acts on the piston I8. Since the piston I9 1s onlyexposed to the accumulator pressure, the piston I8 causes the rockingmember of the control .apparatus iti to tilt, so that water underpressure enters the cylinder 6 and the press 20 piston I is moved so asto perform the casting operation.

On the foot lever I4 of the control apparatus B being released and areversal of its valves thus taking place, the piston 3 will move upwardsun- 25 der the action of the constant accumulator pressure, therebyreleasing the adjusting lever I6, whereby the large piston space of thepressure intensifier t is set to discharge. The pressure in the cylinderI'I and consequently the pressure on 30 the piston I8 is thereby alsoreduced, the piston I9 moves the rocking member of the control apparatusIIJ in the opposite direction to that in which it was previously movedand the cylinder 6 is set to discharge. The press piston 1 moves 35downwards under the action of the constant accumulator pressure.

It is of advantage to place the cylinder I2 which is required forclosing the mould and is actuated by the two-valve control apparatus IIalso under 40 the inuence of the high pressure produced in the pressureintensifier 5 and thus to obtain the requisite high closing force withthe use of relatively small piston surfaces, since through the actuationof the foot lever I4 of the control ap- 45 paratus 8 and the positiveactuation of the control apparatus 9 the desired increase in pressure isproduced not only in the cylinder fi, but also in the cylinder I2.

l claim:

In a hydraulically driven die-casting machine, a press chamber, aremovable closure piece for the press chamber, a mold separate from thevpress chamber, a piston arranged for feeding the casting material underpressure from the chamber into 5";

the mold, the said closure piece maintaining the press chamber closedduring the pressure stroke of the piston, a cylinder, a piston in saidcylinder for raising the closure piece from the press chamber and forclosing the latter and maintaining it in closed condition during thecasting under pressure, the combination with a pressure intensifier,control apparatus for controlling the pressure intensier, the controlapparatus being operable by the closure piece shortly before the latterhas reached itsclosing position to subject the closure member to thepressure of the pressure intensier, and a second control apparatuscontrolled by the said pressure lntensier to control the castingpressure stroke of the press piston in the press chamber.

JOSEF POLK.

